Adaptable multi zone carrier

ABSTRACT

A substrate carrier having a deformable surface for receiving a substrate. Non annular pressure application zones apply pressure to the deformable surface, and addressable transducers within the pressure application zones receive a signal and applying a selectable amount of pressure in response to the signal. In this manner, the amount of pressure provided by the substrate carrier differs from one portion of the substrate to another in a selectable manner. Thus, the pressure applied to the substrate can be tailored to the non uniform thickness of the layer that is being thinned. In other words, portions of the substrate where the layer is thicker can be pressed upon with a greater force by the substrate carrier, thus urging the substrate more forcefully into the polishing pad in those portions, and thereby removing material from the layer at a greater rate of speed in those portions. Similarly, portions of the substrate where the layer is thinner can be pressed upon with a lesser force by the substrate carrier, thus urging the substrate less forcefully into the polishing pad in those portions, and thereby removing material from the layer at a reduced rate of speed in those portions. In this manner, substrates having layers of non uniform thickness can be processed such that the resulting thickness of the thinned layer is extremely uniform.

FIELD

[0001] This invention relates to the field of integrated circuit processing. More particularly, this invention relates to tooling used for handling integrated circuits in wafer form.

BACKGROUND

[0002] Integrated circuits such as those formed in silicon, germanium, or III-IV compounds are typically fabricated as a batch of devices on a common substrate, commonly referred to as a wafer. Wafers typically vary in size from about six inches to about twelve inches in diameter. Although wafers can be smaller or larger than this, most wafers currently used for the production of integrated circuits fall within this range of sizes.

[0003] As the wafers are processed, the various layers which form the elements of the integrated circuits are created. Such processes included, for example, deposition processes where a layer of material is deposited across the surface of the wafer, etch processes where portions of a deposited layer or other material are removed, and doping processes where an atomic dopant is impregnated through the surface of the wafer and buried within the substrate. It is appreciated that there are other processes to which the wafer is also subjected, and many variations on these general process types.

[0004] Most processes tend to have some level of spatial variation, in that they produce somewhat non uniform results as measured across the surface of the wafer. For example, a non uniform etch process may remove more material from an upper layer in first portions of the substrate, and less material from the upper layer in second portions of the substrate. Thus, during such an etching process, the etching of the upper layer in the first portions will achieve the desired end point before the etching of the upper layer in the second portions does. Similarly, a non uniform deposition process deposits material faster in first portions of the substrate, and deposits material slower in second portions of the substrate. Thus, the material is deposited to the desired end point in the first portions of the substrate sooner than it is in the second portions of the substrate.

[0005] Many different methods are used to reduce the degree of non uniformity of the various processes used to fabricate integrated circuits. Unfortunately, it is an elusive goal to completely remove non uniformity from a given process. Adding to the problem is the fact that non uniformity can multiply through the process sequence by which the integrated circuits are fabricated. For example, a non uniformity of a first layer can be further compounded by a non uniformity of a second layer. Similarly, the non uniformity of a first process can be further compounded by a non uniformity of a second process.

[0006] As a more specific example, one method by which a layer of material is thinned on a substrate is called chemical mechanical polishing. During chemical mechanical polishing, the back of the substrate is held with a substrate carrier and the face of the substrate is brought into contact with a rotating polishing pad. A slurry, typically containing both chemical and physical etchants, is applied and the surface of the substrate is eroded as the surface of the substrate and the polishing pad are moved relative to one another. Most preferably the layer of material on the surface of the substrate is removed at an even rate across the surface of the substrate so that a uniform thickness in the layer of material is simultaneously achieved across the entire surface of the substrate.

[0007] Unfortunately, non uniformities in the chemical mechanical polishing process tend to work against the goal of achieving a thinned layer having a perfectly uniform thickness. Further compounding the problem is the fact that the layer of material as formed or deposited is typically non uniform to begin with, in that the thickness of the layer to be thinned was not uniform at the beginning of the process. In such a case, even when the chemical mechanical polishing process removes material at a uniform rate across the entire surface of the substrate, the resultant layer will not have a uniform thickness at the end of the process because it did not start the chemical mechanical polishing process with a uniform thickness.

[0008] Thus, there is a continual need for methods and equipment that increase the uniformity of processing across the surface of a substrate as integrated circuits are fabricated.

SUMMARY

[0009] The above and other needs are met by a substrate carrier according to a preferred embodiment of the present invention. The substrate carrier has a deformable surface for receiving a substrate. Non annular pressure application zones apply pressure to the deformable surface, and addressable transducers within the pressure application zones receive a signal and applying a selectable amount of pressure in response to the signal.

[0010] In this manner, the amount of pressure provided by the substrate carrier differs from one portion of the substrate to another in a selectable manner. Thus, the pressure applied to the substrate can be tailored to the non uniform thickness of the layer that is being thinned. In other words, portions of the substrate where the layer is thicker can be pressed upon with a greater force by the substrate carrier, thus urging the substrate more forcefully into the polishing pad in those portions, and thereby removing material from the layer at a greater rate of speed in those portions. Similarly, portions of the substrate where the layer is thinner can be pressed upon with a lesser force by the substrate carrier, thus urging the substrate less forcefully into the polishing pad in those portions, and thereby removing material from the layer at a reduced rate of speed in those portions. In this manner, substrates having layers of non uniform thickness can be processed such that the resulting thickness of the thinned layer is extremely uniform.

[0011] In various preferred embodiments of the invention, the deformable surface is either a metal fabric or an elastomer, or a combination of the two. The non annular pressure application zones are preferably disposed in a grid pattern. Most preferably, each of the non annular pressure application zones is between about one square millimeter and about six hundred square millimeters in size. In alternate embodiments the addressable transducers are either solenoids or piezoelectric transducers. Most preferably, the addressable transducers comprise digitally addressable devices.

[0012] In an especially preferred embodiment, pressure transducers are disposed within each of the pressure application zones. The pressure transducers sense pressures applied from the substrate to the substrate carrier during processing, and send pressure signals to a controller. The controller receives the pressure signals and individually and selectively controls the addressable transducers based at least in part on the pressure signals. Thus, in this embodiment there is real time feedback to the system for dynamically adjusting the polishing rate in different portions of the substrate, thereby continuously compensating for process variations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Further advantages of the invention are apparent by reference to the detailed description when considered in conjunction with the figures, which are not to scale so as to more clearly show the details, wherein like reference numbers indicate like elements throughout the several views, and wherein:

[0014]FIG. 1 is a functional block diagram representing a chemical mechanical polisher holding a substrate with a substrate carrier according to a preferred embodiment of the present invention,

[0015]FIG. 2 is a top plan view of the substrate carrier according to a preferred embodiment of the present invention, and

[0016]FIG. 3 is a topographical depiction of a substrate with a layer that has a non uniform thickness profile.

DETAILED DESCRIPTION

[0017] Referring now to FIG. 1, there is depicted a functional block diagram of a chemical mechanical polisher 10 holding a substrate 16 with a substrate carrier 12 according to a preferred embodiment of the present invention. The chemical mechanical polisher 10 thins a layer on the surface of the substrate 16 as described above, by holding the surface of the substrate 16 against a rotating polishing pad 26. Both the mechanical action of the pad and the chemical and mechanical action of the slurry that is introduced cause the material at the surface of the substrate 16 to be eroded from the substrate 16, thereby thinning the layer. As mentioned above, it is desirable to remove as much non uniformity from the process as possible, so as to produce a layer that has as uniform a thickness as possible.

[0018] To this end, the substrate carrier 12 includes a deformable surface 14 that receives the substrate 16. The deformable surface 14 may also include means whereby the substrate 16 is retained to the substrate carrier 12, such as electrostatic means, or such retaining means may be otherwise provided, such as clamps that engage a portion of the substrate 16. The deformable surface 14 is preferably formed of a durable material that is both somewhat resistant to the chemical and physical environment of the chemical mechanical polisher 10.

[0019] For example, the deformable surface 14 is preferably resistant to the chemicals in the slurry, and is also reasonably resilient to the abrasive particles in the slurry and the pressures that are exerted between it and the substrate 16, as described in more detail hereafter. Furthermore, the deformable surface 14 is preferably formed of a material that is not a source of contamination to the slurry or the substrate 16, or to the devices that are formed on the substrate 16. In a most preferred embodiment, the deformable surface 14 is formed of a metal fabric or an elastomer.

[0020] The deformable surface 14 of the substrate carrier 12 is preferably logically divided into pressure application zones 28, as depicted in FIG. 2, which depicts the substrate carrier 12 of FIG. 1, such as from a view looking up at the deformable surface 14. The lines on the deformable surface 14 are representational of the logical divisions between different pressure application zones 28, and would preferably not be visible in an actual implementation of the substrate carrier 12. In other words, the orthogonal lines are present so as to better convey the concept of the pressure application zones 28, and do not represent a physical aspect of the substrate carrier 12.

[0021] The pressure application zones 28 represent a position on the deformable surface 14 of the substrate carrier 12 where pressure can be individually and selectively applied by the substrate carrier 12 through the deformable surface 14 and against the substrate 16. This pressure is most preferably applied such as by moving the deformable surface 14 toward the substrate 16 within a given one of the pressure application zones 28 relative to other neighboring pressure application zones 28. Thus, if one pressure application zone 28 sticks out further toward the substrate 16 than its eight nearest neighbor pressure application zones 28, for example, it is said that that one pressure application zone 28 is exerting a greater pressure on the substrate 16 than are the eight nearest neighbor pressure application zones 28.

[0022] The pressure application zones 28 are not disposed in an annular pattern, such as two, three, four, or more concentric rings in a bulls-eye configuration, but are rather preferably disposed in a grid pattern as depicted in FIG. 2. In this manner, the patterns of pressure that can be applied by the pressure application zones 28 are far more configurable than could be had with an annular pattern of concentric rings. Most preferably the pressure application zones 28 each have a surface area of between about one square millimeter and about six hundred square millimeters in size.

[0023] The size that is selected for each pressure application zone 28 represents a balance between different competing parameters. For example, for very large substrates 16, such as those that are about three hundred millimeters in diameter and larger, pressure application zones 28 on the larger end of the range given above may be most appropriate, as a finer degree of control may not be needed. On the other hand, even with such large substrates 16, if there is a large variation in the thickness of the layer to be thinned during the chemical mechanical polishing process, then smaller pressure application zones 28 may be desired so as to provide a finer degree of control over the thinning of the layer.

[0024] Similarly, for very small substrates 16, such as those that are about seventy-five millimeters in diameter and smaller, pressure application zones 28 on the smaller end of the range given above may be most appropriate, as they would tend to provide more control over the thinning process within the smaller substrate 16. However, even with such small substrates 16, if there is only a very small variation in the thickness of the layer to be thinned during the chemical mechanical polishing process, then larger pressure application zones 28 may be desired, because a finer degree of control over the thinning of the layer may not be required.

[0025] The pressure that may be so applied in each of the pressure application zones 28 is preferably provided by addressable transducers 18 that are disposed within each of the pressure application zones 28. In one embodiment the addressable transducers 18 are solenoids, and in an alternate embodiment the addressable transducers 18 are piezoelectric transducers. Preferably, the transducers 18 are digitally and individually selectable, as described in more detail hereafter.

[0026] To continue briefly a topic that was introduced above, the size of the pressure application zones 28 may also be determined at least in part upon the type of transducer 18 that is employed within each pressure application zone 28, in that some transducers 18 may be smaller than others and may fit more readily within smaller pressure application zones 28, and other transducers 18 may be larger than others and may fit more readily within larger pressure application zones 28. The size of the pressure application zones 28 may also depend at least in part upon the size and presence of other elements that are to be disposed within each of the pressure application zones 28, as described in more detail below. It is appreciated that not all of the pressure application zones 28 need be of the same size or shape.

[0027] The pressure applied by the addressable transducers 18 is preferably controlled by a controller 24, as depicted in FIG. 1, which may reside in either the main part of the chemical mechanical polisher 10 or within the substrate carrier 12, and which communicates with the addressable transducers 18 via line 22. One reason why it is preferred that the addressable transducers 18 be digitally selectable is so that fewer lines 22 are required to individually select the addressable transducers 18, and thus the lines 22 do not require much room in the arm 36. This is beneficial because it is desirable to not increase the size of the arm 36 to accommodate a large bundle of lines 22, and also because the substrate carrier 12 preferably rotates on the end of the arm 26, and connections for many lines 22 through the rotating connections would be expensive and complicated.

[0028] Within each pressure application zone 28 there is also preferably disposed a pressure transducer 20, which senses the pressure applied from the substrate 16 to the substrate carrier 12 during processing. To explain more fully, as the substrate 16 is pressed against the polishing pad 26 by the substrate carrier 12 during processing, the substrate 16 in effect presses back against the substrate carrier 12. The pressure transducers 20 sense the force of the pressure of the substrate 16 against the deformable surface 14, and generate signals representing the force of that pressure, which are preferably sent back to the controller 24 along the lines 22. The benefit of this preferred embodiment is discussed in more detail hereafter.

[0029] With reference now to FIG. 3, there is depicted a topographical representation of the surface of a substrate 16, showing first portions 30, second portions 32, and third portions 34. The pattern of the various portions of the substrate 16 is representative only, and is not intended to limit the invention in any way. The pattern represents a varying thickness of a layer that is deposited or formed on the surface of the substrate 16. For example, portion 30 could be those sections of the layer that have a thickness within a first thickness range, portion 32 could be those sections of the layer that have a thickness within a second thickness range, and portion 34 could be those sections of the layer that have a thickness within a third thickness range.

[0030] For the purposes of example herein, it is specified that portion 30 is the section of the substrate 16 where the layer is the thinnest, portion 34 is the section of the substrate 16 where the layer is the thickest, and portion 32 is the section of the substrate 16 where the layer has an intermediate thickness. Such deposition patterns as represented in FIG. 3 may be caused, for example, by a non uniform gas flow within a deposition chamber, a non uniform heating of the substrate 16 during deposition, a non uniform energy field during deposition, or a combination of these or other variables.

[0031] Regardless of the cause or the exact pattern of the non uniform layer thickness, it is desirable to thin the layer to a uniform thickness across the surface of the substrate 16 during the chemical mechanical polishing process. The various embodiments of the invention as described and claimed herein are particularly adapted to achieving that goal. For example, if the pattern of non uniformity, as exemplified in FIG. 3, is consistent from substrate 16 to substrate 16, or in other words the pattern of non uniformity does not change much from substrate 16 to substrate 16, then the substrate carrier 12 can be programmed by the controller 24 so that the addressable transducers 18 press harder against the deformable surface 14 in those pressure application zones 28 that underlie the portions 34 where the layer is the thickest. In this manner, because the substrate 16 is preferably somewhat flexible, the portions 34 are pressed with a greater force into the polishing pad 26 during the chemical mechanical polishing process, and thus tend to be eroded at a greater rate than other portions of the substrate 16.

[0032] Similarly, the substrate carrier 12 can be programmed by the controller 24 so that the addressable transducers 18 press with slightly less force against the deformable surface 14 in those pressure application zones 28 that underlie the portions 32 where the layer is of intermediate thickness. In this manner, the layer in the portions 32 is eroded somewhat less vigorously during the chemical mechanical polishing process than it is in the portions 34. Thus, over the length of time that the chemical mechanical polishing process is performed, the layer can be thinned to the same thickness in both the portions 32 and the portions 34.

[0033] In a similar vein, the substrate carrier 12 can be programmed by the controller 24 so that the addressable transducers 18 press with an even lesser degree of force against the deformable surface 14 in those pressure application zones 28 that underlie the portions 30 where the layer is the thinnest. Thus, at the end of the process, the thickness of the layer can be the same thickness in all of the different portions of the substrate 16.

[0034] Although the above configuration is useful, it is appreciated that there are some difficulties in its use. For example, although the non uniformity of the thickness of the layer across the surface of the substrates 16 may be quite similar from substrate 16 to substrate 16, it is not often exactly the same, and thus small variations in the programming of the substrate carrier 12 would be preferred. These small programming variations may be time consuming and thus expensive to accomplish for each substrate 16. In addition, learning exactly how hard a given addressable transducer 18 should press against the substrate 16 in order to compensate for a given layer thickness is also a time consuming proposition. However, even those these issue may consume a certain amount of time and effort, they can be accomplished and the substrates 16 can be processed with a greater degree of uniformity.

[0035] However, with the addition of the pressure transducers 20, many of these issues can be reduced in scope. When the substrate 16 is held against the polishing pad 26 by the substrate carrier 12, those portions of the substrate 16 where the layer is relatively thicker tend to contact the polishing pad 26 before those portions of the substrate 16 where the layer is relatively thinner. Thus, as the substrate 16 is pressed against the polishing pad 26, the substrate 16 tends to exert a greater pressure against the substrate carrier 12 in those portions of the substrate 16 where the layer is relatively thicker.

[0036] As a specific example, and with reference to FIG. 3, portions 34 of the substrate 16 tend to press against the deformable surface 14 of the substrate carrier 12 with a greater force than do portions 32, which tend to press against the deformable surface 14 of the substrate carrier 12 with a greater force than do portions 30. Thus, the pressure transducers 20 can detect from moment to moment those portions of the substrate 16 that have a relatively thicker layer remaining. The pressure transducers 20 preferably generate signals in response to such sensed pressure, which are sent back to the controller 24 as described above. The controller 24 then uses those signals as a feed back to determine which of the addressable transducers 18 should be instructed to press harder against the substrate 16, so as to cause those relatively thicker portions of the substrate 16 to erode faster. In this manner, a dynamic feed back system is instituted which can automatically adapt to the non uniformities of a starting substrate 16, and also to the non uniformities that may be introduced during the chemical mechanical polishing process itself.

[0037] Most preferably there is a single pressure transducer 20 associated with each single addressable transducer 18 within each pressure application zone 28. However, it is appreciated that many other configurations are possible. For example, there may be several addressable transducers 18 for each pressure transducer 20. In this manner, the additional addressable transducers 18 can be used to interpolate the pressure between adjacent pressure transducers 20. Likewise, there may be several pressure transducers 20 for each addressable transducer 18, which may be used to apply a pressure based upon an average of the pressure readings from the pressure transducers 20, for example.

[0038] The foregoing embodiments of this invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments are chosen and described in an effort to provide illustrations of the principles of the invention and its practical application, and to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as is suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled. 

What is claimed is:
 1. In a substrate carrier of the type used for retaining a substrate during chemical mechanical polishing, the improvement comprising: a deformable surface for receiving the substrate, non annular pressure application zones for applying pressure to the deformable surface, and addressable transducers within the pressure application zones for receiving a signal and applying a selectable amount of pressure in response to the signal.
 2. The substrate carrier of claim 1, wherein the deformable surface comprises a metal fabric.
 3. The substrate carrier of claim 1, wherein the deformable surface comprises an elastomer.
 4. The substrate carrier of claim 1, wherein the non annular pressure application zones are disposed in a grid pattern.
 5. The substrate carrier of claim 1, wherein each of the non annular pressure application zones is between about one square millimeter and about six hundred square millimeters in size.
 6. The substrate carrier of claim 1, wherein the addressable transducers comprise solenoids.
 7. The substrate carrier of claim 1, wherein the addressable transducers comprise piezoelectric transducers.
 8. The substrate carrier of claim 1, wherein the addressable transducers comprise digitally addressable devices.
 9. The substrate carrier of claim 1, further comprising pressure transducers disposed within each of the pressure application zones, the pressure transducers for sensing pressures applied from the substrate to the substrate carrier during processing.
 10. The substrate carrier of claim 1, further comprising a controller for individually and selectively controlling the addressable transducers.
 11. The substrate carrier of claim 1, further comprising: pressure transducers disposed within each of the pressure application zones, the pressure transducers for sensing pressures applied from the substrate to the substrate carrier during processing, and for sending pressure signals, and a controller for receiving the pressure signals and individually and selectively controlling the addressable transducers based at least in part on the pressure signals.
 12. In a substrate carrier of the type used for retaining a substrate during chemical mechanical polishing, the improvement comprising: a deformable surface for receiving the substrate, non annular pressure application zones for applying pressure to the deformable surface, and addressable transducers disposed in a grid pattern within the pressure application zones for receiving a signal and applying a selectable amount of pressure in response to the signal, wherein each of the non annular pressure application zones is between about one square millimeter and about six hundred square millimeters in size.
 13. The substrate carrier of claim 12, wherein the addressable transducers comprise digitally addressable devices.
 14. The substrate carrier of claim 12, further comprising pressure transducers disposed within each of the pressure application zones, the pressure transducers for sensing pressures applied from the substrate to the substrate carrier during processing.
 15. The substrate carrier of claim 12, further comprising: pressure transducers disposed within each of the pressure application zones, the pressure transducers for sensing pressures applied from the substrate to the substrate carrier during processing, and for sending pressure signals, and a controller for receiving the pressure signals and individually and selectively controlling the addressable transducers based at least in part on the pressure signals.
 16. In a substrate carrier of the type used for retaining a substrate during chemical mechanical polishing, the improvement comprising: a deformable surface for receiving the substrate, non annular pressure application zones for applying pressure to the deformable surface, and addressable transducers disposed in a grid pattern within the pressure application zones for receiving a signal and applying a selectable amount of pressure in response to the signal, wherein the addressable transducers are digitally addressable devices.
 17. The substrate carrier of claim 16, wherein each of the non annular pressure application zones is between about one square millimeter and about six hundred square millimeters in size.
 18. The substrate carrier of claim 16, further comprising pressure transducers disposed within each of the pressure application zones, the pressure transducers for sensing pressures applied from the substrate to the substrate carrier during processing.
 19. The substrate carrier of claim 16, further comprising a controller for individually and selectively controlling the addressable transducers.
 20. The substrate carrier of claim 16, further comprising: pressure transducers disposed within each of the pressure application zones, the pressure transducers for sensing pressures applied from the substrate to the substrate carrier during processing, and for sending pressure signals, and a controller for receiving the pressure signals and individually and selectively controlling the addressable transducers based at least in part on the pressure signals. 